Japanese Patent Application Publication No. S60-116294 describes a television conference system, which displays an image indicating a level of sounds picked up by a microphone that is provided for each of meeting attendants. With the display of the level of sounds output by each attendant, the attendants are able to know who is currently speaking or the level of voices of each attendant. This system, however, has drawbacks such that a number of microphones has to be matched with a number of attendants to indicate the sound level for each attendant. Since the number of attendants will be different for each meeting, it has been cumbersome to prepare every microphone for each attendant.